Proofing of iron and steel against rust



Patented July 2, i929.

UNITED STATES WILLIAM HOWARD COLE, OF PARIS, FRANCE.

PROOFING OF IRON AND STEEL AGAINST RUST.

. R0 Drawing. Application filed March 11, 1929, Serial No. 346,249, and in Great Britain January 29, 1929,

This invention is an improvement in or modification of the inventions described and claimed in my applications for Letters Patent Ser. Nos. 171,730 and 171,731. In the said specifications I have described new processes for proofing iron and steel against rust consisting in efi'ecting a deposit on the articlesproofed by treating them under the conditions described with a special solution of. phosphates of, aluminium, zinc, iron and chromium. The present invention relates to a select-ion of conditions and proportions included in my said prior specifications, but which I have found, upon further experiment, togive the best possible result.

According to my invention, I provide a process for the proofing of iron and steel against rust, substantially. as claimed in specifications Ser. No. 171,730, in which iron, zinc, chromium and aluminium are used.

To make the processing solution I use:

Iron filings (clean and free from scale), zinc powder, aluminium powder, and chro mium powder. i

It is a feature of the present invention that these are dissolved separately at a temperature not over 90 C. in a solution of phosphoric acid B. diluted with water to 22 B. until the said metallic phosphatic solutions are each of a density of 36 B.

In dissolving, the temperature should be retained as constant as possible during the whole time of dissolution but in no instance should it go above 90 C. and during said period of dissolution the containers should be covered in order to save any lossfrom evaporation.

These four solutions at thesaid 36 B. are then mixed together in the following proportions 1 part aluminium solution, 5 parts zinc solution, 5 parts iron solution, part chromium solution.

In place of chromium powder, chromium oxide may be used for economical reasons as being less expensive, takes less time for dissolution and, further, I find no material difference in the results.

To this mixture is then added a solution or mixture of the followingingredients and in the proportion hereinafter described:-

25 grammes bichromate of potassium, V

grammes neutral chromate of potassium,25 grammes monobasic phosphate of ammonium, 5 grammes naphthalene.

' This mixture is dissolved or suspended in 1ai-eof water (distilled water is preferable) 4 cubic centimetres of this solution or susof the operation.

The addition of these ingredients has for] its purpose to obtain the full value of the combination of .metals; In my view they act as follows:--

Bichromate of potassium gives cementa- 'tion effect of the combined precipitated mass when it attacks the iron or steel surfaces.

Neutral chromate of potassium creates a special aflinity between the four metals after they have been dissolved. The use of chromium gave a considerable amount of .trouble in'uniting with the other metals in solution after they were dissolved, and I- found that this ingredient had a decided cohesive influence, as between the chromium and the other metals.

Monobasic phosphate of ammonium holds for an instant the final combination of the precipitants until all of the metals have been thrown down. a Naphthalene is .used principally in that itaids in the union of the combined precipitants on to the surface of the articles treated. i

The stock liquor may be used direct for processing, after being diluted to about 3 B. or it may be evaporated down, to salts or a compound (as I call it), for ease in handling or transportation.

In evaporating over heat, care must be taken that it is never done above atemperature over C. and, that care must be'taken so as not to permit of its burning. It is advisable that constant stirring be done during evaporation.

The salts or compound is ready for processing B V I For processing, the solution at about 3 B. is placed in any. suitable tank, preferby simply mixing with water to about.

ably closed, so as to permit of a pressure within, and heated to a temperature around the boiling point but above 90 C. and preferably about 95 C.

It will be noted that the processing operation is etiected at a temperature higher than that at which the metals are dissolved. appears as if a certain amount of acid became free or active under the higher temperature of processing and this appears to be necessary for a successful operation in the process.

Into this are placed the iron or steel articles (preferably in a suitable container or cage) and allowed to remain from 1 to 1 hours. The temperature should be constant during the operation.

There should preferably be a constant change oi contact of the articles being treated during the processing operation.

Before processing, articles to be treated should be as clean as possible and free from rust, scale and dirt.

It is advisable to have sufficient solution in excess in the processing tank. It is recom mended that this be at least 1 to 2 times the quantity necessary, although a greater amount does not harm.

Both before and after processing, the solution in the tank should be measured, so that the solution may be properly adjusted for the next operation of processing.

orated during the process and then sufficient stock liquor is also added to bring the solution to the original operating specific gravit It will be understood that good results can be obtained Whilst departing from the quantities of metals and other ingredients, varying the stated temperatures and densities, but I have found that the best results are obtained by observing the conditions herein described, which are selected from, and'in some respects modifications of, my specifications Ser. No. 171,730.

lVhat I claim and desire to secure by Let ters Patent is 1. The improvement in proofing of iron and steel against rust, which consists in preparing the processing solution from the four metals, iron, zinc, alumlnunn and Sufficient water is added to take the place of that evapand steel against rust, which consists in preparing the processing solution as claimed in claim 1, and adding to it a small'quantity of a solution or suspension containing bichromate oi potassium, neutral chromate of potassium, monobasic phosphate of ammonium and naphthalene in the proportions grammes bichromate of potassium, grammes neutral chromate of potassium, 25 grammes monobasic phosphate of ammonium, and 5 grammes of napthalene.

3. The improvement in the process of proofing iron and steel against rust comprising the preparing of a processing solution of iron, zinc, aluminum and chromium dissolved separately in a solution of phosphoric acid and then combining the same, diluting this solution with water to about 3 degrees Be. and then treating the articles to be proot'ed with this resulting solution at about 95 degrees C. which temperature is higher than that at which the metals were dissolved in solution.

4. In combination in a compound for rustproofing of metal, comprising a solution of phosphoric acid having one part aluminum. live parts zinc, five parts iron and one-half part. chromium.

In combination in a compound for rustproofing of metal, comprising a solution of phosphoric acid having one part aluminum, five parts zinc, five parts iron and one-half part chromium, and a second solution comprising 25 grammes bichromate of potassium, 7 0 grammes neutral chromate of potassium, 25 grammes monobasic phosphate of ammonium and 5 grammes of naphthalene.

In testimony whereof, I afiix my signature.

WILLIAM HOWARD COLE. 

